Cardiac arrhythmias disrupt normal heart rhythm and cardiac efficiency. These arrhythmias can be treated using, for example, pulsed field ablation (PFA) or radiofrequency (RF) ablation. The delivery of ablation therapy involves the use of a set of components that requires a reliable electrical pathway for the two-way transmission of electrical signals. These components include: an energy source in the form of pulsed or continuous wave signals such as a pulsed electric field or pulsed RF generator, an ablation delivery catheter that applies PFA or pulsed RF energy to intended endocardial locations in the heart; a catheter electrode distribution system (CEDS); and a set of interconnecting cables.
The CEDS performs the signal adjudication task similar to that of a centralized telephone system in that it prevents mutual interference due to the co-mingling of high energy ablation and very low-energy patient-borne signals. In the downstream case, ablation energy is intended to travel from equipment to the patient, whereas signals that originate at the intracardiac catheter electrodes travel to operating room monitoring equipment in the upstream case. These upstream signals include contact sensing and lesion assessment impedance, navigation, electrode thermocouple signals, and electrogram (EGM) signals.
A second function of the CEDS is to adjudicate patient return electrode (PRE) connections. The PRE is an electrical large area grounding connection to the body generally used when unipolar energy is delivered from an intracardiac catheter with a small electrode surface area relative to the surface area of the PRE. It normally consists of an electrically conductive patch applied to a posterior location such as the patient's lower back. For example, some equipment may require a PRE connection, whereas other items may not or should not. In the case of contact sensing and lesion assessment, a monitoring instrument may require a unipolar or PRE path to render information regarding catheter electrode contact and lesion quality. On the one hand, PFA or pulsed RF bipolar ablation energy should not have a patient reference connection other than the two bipolar connections in the intracardiac treatment volume, whereas unipolar PFA or pulsed RF ablation energy requires a PRE to return treatment energy back to the generator. Therefore, the CEDS is required to “make” PRE contact during sensing and then “break” PRE contact during bipolar PFA or bipolar pulsed RF ablation.
Further, PFA and pulsed RF each involve the use of high energy in the form of current, voltage, or combinations thereof. As such, the delivery pathway may be vulnerable to degradation and eventual failure. The most likely pathway failure is one that occurs in the catheter, primarily because of the failure of very small-gauge wires within the catheter shaft or failure of the insulation on those wires. The diameter of the catheter shaft is severely constrained by the catheter electrical therapy delivery lumen, which places a limit on the size and quantity of the wires that may be used. During PFA or pulsed RF treatment delivery, the very small-gauge wires are vulnerable to heating and arcing. While a properly designed catheter used in a routine cardiac ablation procedure can be expected to provide nominal performance, a procedure requiring significantly longer time with commensurately greater manipulation may cause the catheter to degrade. Without specific information as to the energy delivery integrity of the pathway, the physician performing a lengthened operation does not know the true condition of the catheter. Thus, the user must either choose to continue delivery treatment energy with a possibly degraded catheter, or decide that the catheter should be exchanged to ensure integrity, which essentially renders the original catheter defective. The second option results in an operation with increased time and expense, as well as increased patient risk. If the user could know specifically the limitations of the potentially degraded or damaged catheter, he or she could proceed and complete the operation and avoid exchange costs and patient risk altogether.
Other than the catheter, other pathway locations may be degraded or damaged. For example, an interconnecting cable may become loose or damaged. It is also possible that the generator delivery section may be degraded or damaged. Another example of failure may occur within the CEDS: a relay used to direct energy may be degraded or damaged (inadvertently latched shut or stuck open). In all of these cases, patient therapy is degraded or ineffective. Worse yet, some of these conditions may pose additional hazards to the patient.